The invention relates to an indicating device, particularly a liquid crystal display, having a fluid which can be switched between two optically different states and which fills a cell chamber formed between two transparent support plates which are parallel to each other, the support plates being held at a predetermined distance apart by a plurality of spacer elements of given size and being each provided with an electrically conductive layer, which layers are located opposite each other.
In such known indicating devices the spacer elements are distributed essentially uniformly over the entire surface of the support plates. They serve to keep the support plates at a given distance from each other since in the event of a reduction of this distance the operability of the indicating device is negatively affected. If such an indicating device, which may be a liquid crystal display, is subjected to very low temperatures, the fluid which is switchable between two optically different states, for instance a liquid-crystal material, contracts.
Since the support plates are held at a predetermined distance from each other by the spacer elements, the volume of the cell chamber remains the same while the volume of the liquid-crystal material is reduced. This leads to the formation of vacuum bubbles at unpredictable places within the cell chamber. If the vacuum bubble is located at a point opposite which there are electrically conductive layers by the control of which the liquid-crystal material can be switched in order to display indication symbols, then display of the indication symbols is not possible since no liquid-crystal material is present there any longer. The display fails.
The vacuum bubbles do break up, it is true, when the liquid-crystal material has again become heated to positive temperatures. However, this is not very helpful in various cases of use of such indicating devices. If such indicating devices are, for instance, installed in the instrument panel of automotive vehicles then they will fail during the entire winter season, particularly in regions having low winter temperatures. Displays in automotive vehicles must be operable at temperatures from -40.degree. C. to +80.degree. C.
The object of the present invention is, therefore, to create an indicating device in accordance with the introductory paragraph whose operability is assured over wide temperature ranges and, in particular, at low temperatures.